6 - (1,2,3,4 - tetrahydro - 2 - thioxo - 4,4,6 - trimethyl - 1 - pyrimidinyl)benzothiazolylthiolcarbonates



United States Patent 6 Claims. (11. 260256.5)

This application is a division of Serial No. 138,296, filed September15, 1961, now Patent No. 3,151,114, September 29, 1964.

The present invention relates to 1,2,3,4-tetrahydro-1- (2mercapto-6-benzothiazolyl)-2-thioxo-4,4,6-trimethylpyrimidine andderivatives thereof.

1,2,3,4 tetrahydro-1-(Z-mercapto-6-benzothiaz-olyl)-2-thioxo-4,4,6-trimethylpyromidine can exist in two tautomeric forms asfollows:

and

( lHa The structure is undoubtedly II predominately. For example adisodium salt does not form. Of course, the same tautomerism is possiblein the mercaptothiazole nucleus but the mercaptan structure is generallyaccepted and is consistent with the chemical properties observed. Thepreparation and properties of this compound are described in detailbelow:

EXAMPLE 1 To a stirred slurry containing 79.0 grams (0.5 mole) of1,1-dirnethyl-3-oxobutylthiocyanic acid, 750 ml. of water and 6 grams ofconcentrated sulfuric acid was added in one portion 91.1 gram-s (0.5mole) of 6-amino-2-mercaptobenzothiazole and the mixture heated at 8090C, for a period of 3 hours. After cooling to 25 C., the precipitate wascollected by filtration, washed with water until the washings wereneutral to litmus, and air-dried at 2530 C.1,4dihydro-1-(Z-mercapto-6-benzothiazolyl)4,4,6-trimethyl-2-pyrimidinethiol (predominately 1,2,3,4- tetrahydro 1(Z-mercapto-6-benzothiazolyl)-2-thioxo-4, 4,6-trimethylpyrimidine) wasobtained in 97.5% yield. After recrystallization from dilute ethylalcohol it melted at 20 7-209 C. Analysis gave 13.07% nitrogen and29.34% sulfur compared to 13.07% nitrogen and 29.72% sulfur calculatedfor C H N S This compound accelerates wlcanization of natural andsynthetic rubber and imparts considerable processing safety. It is alsoa valuable intermediate and undergoes reactions typical of those knownfor mercapto'benzothiazole involving the mercaptan radical.

Since the m'ercapto hydrogen in the thiazole ring is active, a varietyof derivatives can be obtained by replac- Patented Dec. 21, 1965 ice ingthe hydrogen by other groups, as for example saltforming groups andorganic radicals. Among the organic radicals which may replace hydrogenare alkyl, alkenyl, halogen substituted alkenyl, dialkylaminoethyl,Z-butenylene, 2-butynyl, 2-propynyl, Z-cyclohexenyl, 2-oxocyclohexyl,5,5,7,7 tetramethyl 2 octenyl, -CH NH groups such as where X is sulfuror oxygen and the valences on the nitrogen may be satisfied by open orclosed chain aliphatic radicals or divalent radicals which with nitrogenconstitute a heterocyclic group, or phenyl,

-(IJIXY groups where X is sulfur or oxygen and Y is lower alkyl oralkenyl,

and chlorophenoxyacetyl. These, of course, are only illustrative of afew of the possible derivatives. All of them accelerate vulcanization toa greater or less degree. Replacing mercapto hydrogen with radicalswhich inactivate mercaptobenzothiazole do not appear to have the sameeffect on the product of Example 1. The term free mercaptan hereinafterdesignates the product of Example 1.

Thiolcarbonates In the preparation of thiolcarbonates the solutioncontained 32.2 grams (0.1 mole) of free mercaptan, 6.3 grams (0.1 mole)of potassium hydroxide, 500ml. of acetone and 10 ml. of water. Inaddition, the reaction mixture was stirred at 25-30" C. for 24 hours.Following is illustrative of this group:

S [6 (1,2,3,4 tetrahydro-2-thioxo-4A,6-trimethyl-1-pyrimidinyl)-2-benzothiazolyl] O-ethylthiolcarbonate in 86.2% yield fromethyl chloroformate. The product was a yellow-green solid melting at127-129 C. after recrystallization from ethyl alcohol. Analysis gave10.02% nitrogen and 24.49% sulfur compared to 10.68% nitrogen and 24.44%sulfur calculated for C H N O S S [6 (l,2,3,4tetrahydro-2-thioxo-4,4,6-trimethyl-lpyrimidinyl)-2-benzothiazoly1]O-methylthiolcarbonate in 79.2% yield from methyl chloroformate. Theproduct was a brown solid melting at -122 C. after recrystallizationfrom ethyl alcohol. Analysis gave 10.26% nitrogen and 25.00% sulfurcompared to 11.07% nitrogen and 25.35% sulfur calculated for C H N O S S[6 (1,2,3,4tetrahydro-2-thioxo4,4,6-trimethyl-lpyrimidinyl)-2-benzothiazolyl]O-isopropylthiolcarbonate in 83.8% yield from isopropyl chloroformate.The prod uct was a brown solid melting at 156-15 8 C. afterrecrystallization from ethyl alcohol. Analysis gave 9.78% nitrogencompared to 10.31% calculated for *C H N O S S [6 (1,2,3,4tetrahydro-2-thioxo-4,4,6-trimethyl-1- pyrimidinyl)-2-benzothiazolyl]O-pentylthiolcarbonate in 45.9% yield from amyl chloroforrnate. Theproduct was a tan solid melting at 142-144 C. after recrystallizationfrom alcohol/ acetone. Analysis gave 9.95% nitrogen and 21.79% sulfurcompared to 9.65% nitrogen and 22.08% sulfur calculated for C H N O SO-allyl S- 6-( 1,2,3 ,4-tetrahydro-2-thioxo-4,4,6-trimethyl 1pyrimidinyl) 2 benzothiazolyl]thiolcarbonate in 14.9% yield from allylchloroformate. The product was a tan solid melting at 133 C. withdecomposition. Analysis gave 10.58% nitrogen compared to 10.36%calculated fOl' C H1gN302S3.

3 0,0 oxydiethylene bis{S [6 (1,2,3,4-tetrahydro-2- thioxo 4,4,6trimethyl-l-pyrimidinyl)-2-benzothiazolyl] thiolcarbonate} in 87.5%yield from one-half mole of (011201120 (HICDZ The product was a tansolid melting at 108 C. with decomposition. Analysis gave 9.98% nitrogencompared to 10.49% calculated for C H N O S 0,0-ethylenebis{S-[6-(1,2,3,4-tetrahydro-2-thioxo-4,4, 6 trimethyl-l-pyrimidinyl-2-benzothiazolyl] thiolcarbonate} in 87.0% yield from one-half mole ofThe product was a yellow solid melting at 135 C. with decomposition.Analysis gave 10.66% nitrogen compared to 11.10% calculated for C H N OS S-methyl S [6-(1,2,3,4tetrahydro-2-thioxo-4,4,6-trimethyll-pyrimidinyl)-2-benzothiazolyl]dithiolcarbonate in 93% yield frommethyl chlorothiolformate. In this preparation 300 ml. of acetone andml. of water were employed to prepare the solution of free mercaptan.The product was a brown solid melting at 146148 C. Analysis gave 10.67%nitrogen compared to 10.62% calculated for c 3I'I 7N OS4.

Ethyl 6-(1,2,3,4-tetrahydro-2-thioxo-4,4,6-trimethyl-1-pyrimidinyl)-2-benzothiazolyldithiolcarbonate in 90.5% yield from ethylchlorothiolformate. Again 300 ml. of acetone and 10 ml. of water wereemployed to prepare the solution of free mercaptan. After stirring at C.for 24 hours, 300 ml. of water and 500 m1. of ethyl ether were added,stirring continued for 15 minutes and the reaction mixture filtered toremove a small amount of impurities. The ether layer was separated,washed with water until the washings were neutral to litmus and driedover sodium sulfate. Upon removal of ether in vacuo, a brown solidresulted melting at 135- 137 C. after recrystallization from ethylalcohol. Analysis gave 10.63% nitrogen and 30.75% sulfur compared to10.26% nitrogen and 31.31% sulfur calculated for C1'7H19N3OS4.

As further illustrative of the invention, natural rubber tread stockswere compounded comprising:

Parts by weight Smoked sheets rubber a- 100.0 Carbon black 50.0 Zincoxide 5.0 Stearic acid 3.0 Saturated hydrocarbon softener 3.0 Sulfur 2.5Antioxidant 1.0 Accelerator 0.5

The accelerator added to the base stock is indicated below.

Stock AS-[6-(1,2,3,4-tetrahydro-2-thioXo-4,4,6-trimethyl- 1-pyrimidinyl) -2-benzothiazolyl] O-ethylthiolcarbonate BS- 6-( 1 ,2, 3,4-tetrahydro-2-thioXo-4,4,6-trimethyll-pyrimidinyl -2-benzothiazolyl]O-methylthiolcarbonate "CS- [6-(1,2,3,4-tetrahydro-2=thioXo-4,4,6-trimethyll-pyrimidinyl-2-benzothiazolyl] O-isopropylthiolcarbonate DS-[6-(1,2,3,4-tetrahyd'ro-2-thioXo-4,4,6-trimethyl- 1 -pyrimidinyl-2-benzothiazolyl] O-pentylthiolcarbonate E-0,0-oxydiethylene bis{S-[6-(1,2,3,4-tetrahydro- 2-thioxo-4,4,6-trimethyl- 1 pyrimidinyl) -2-benzothiazolyl]thiolcarbonate} F0,0'-ethylene bis{S-[6-(1,2,3,4-tetrahydro-2- thioxo-4,4,6-trimethyll-pyrimidinyl) -2-benzothiazolyl] thiolcarbonate} G-S-methyl S- [6-(1,2,3,4-tetrahydro-2-thioxo- 4,4,6-trimethyll-pyrimidinyl-2-benzothiazolyl] dithiolcarbonate HEthyl6-(1,2,3,4-tetrahydro-2-thioxo-4,4,6-trimethyl-l-pyrimidinyl)-2-benzothiazolyldithiolcarbonate The stockswere cured in the usual manner by heating in a press for differentperiods of time at 144 C. Processing safety of the vulcanizable stockswas evaluated by means of a Mooney plastometer. The figures recordedwere the times required for the Mooney plasticity at C. to rise tenpoints above the minimum value. The modulus and tensile properties ofthe 60 minute cures are recorded;

TABLE I Modulus of elasticity Tensile at Mooney Stock in lbs/in. atbreak in Scorch elongation of 300% lbs/in. at 135 C.

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is:

1.. A compound of the formula Where T is6-(1,2,3,4-tetrahydro-2-thioxo-4,4,6-trimethyll-pyrimidinyl)-2-benzothiazolyl,X is selected from a group consisting of oxygen and sulfur, n is aninteger equal to the valence of R selected from the group consisting ofl and 2 and R is selected from the group consisting of lower alkyl,lower alkenyl, ethylene, and oxydiethylene.

2. Ethyl 6 (1,2,3,4 tetrahydro 2 thioXo 4,4,6 trimethyl 1 pyrimidinyl) 2benzothiazolyldithiolcarbonate.

3. S [6 (1,2,3,4 tetrahydro 2 thioXo 4,4,6 trimethyl 1 pyrimidinyl) 2benzothiazolyl] O-rnethylthiocarbonate.

4. S methyl S [6 (1,2,3,4 tetrahydro 2 thioxo- 4,4,6 trimethyl lpyrimidinyl) 2 benzothiazolyl] dithiolcarbonate.

5. S [6 (1,2,3,4 tetrahydro 2 thioxo 4,6,6 trimethyl 1 pyrimidinyl) 2benzothiazolyl] O-ethylthiolcarbonate.

6. S [6 (1,2,3,4 tetrahydro 2 thioxo 4,4,6 trimethyl 1 pyrimidinyl) 2benzothiazolyl] O-isopropylthiocarbonate.

No references cited.

IRVING MARCUS, Primary Examiner.

NICHOLAS S. RIZZO, Examiner.

1. A COMPOUND OF THE FORMULA